Sealing arrangement for electron discharge devices



Aug. 3, 1965 A. VELTE E'l'AL 3,193,371

SEALING ARRANGEMENT FOR ELECTRON DISCHARGE DEVICES Filed Dec. 15, 1961 INVENTORS' A'VELTE 8r D.GRAULEAU ATTO United States Patent 3,198,371 SEALING ARRANGEMENT FUR ELECTRON DlSCl-IARGE DE'VEQES Andre Velte and Didier Grauleau, Paris, France, assignors to @SF-Cornpagnie Generals de Telegraphic sans Fil, Paris, France Filed Dec. 15, 1% Ser. No. 159,637 Claims priority, application France, Beta 30, 196%), 848,439 5 Claims. (Cl. 22ll2.2)

The present invention relates to vacuum techniques, and is more particularly concerned with the sealing, after pumping, of evacuated enclosures or envelopes having metallic walls as, for example, those of high-power elec tron tubes.

The pumping of envelopes or enclosures to be evacuated takes place most generally, as is known, through the orifice of a small exhaust stem, either of glass or metal and provided within one of the walls of the enclosure or envelope. Once the pumping operation is terminated, the exhaust stem is ordinarily closed by heating the free end thereof to the point of fusion.

For that reason, the exhaust stems used in the prior art devices have to be relatively thin and of small diameter. Consequently, the structures utilizing the prior art exhaust stems can assure only relatively low pumping rates and the structure thereof is mechanically sufficiently fragile.

Additionally, as each exhaust stem can be utilized only a single time, it is necessary, when one desires to make use several times of the same envelope or enclosure, to provide again each time a new stem.

The present invention has as its primary object an improved vacuum-tight enclosure or envelope freed of the shortcomings and inadequacies mentioned hereinabove that are normally encountered with the prior art techniques and structures resulting therefrom.

It is a further object of the present invention to provide a sealing arrangement, particularly for high-power electron discharge devices which provides a pumping orifice of relatively large diameter so as to assure a relatively large pumping rate.

Still another object of the present invention resides in the provision of an obturating structure, particularly for high-power electron discharge devices which is relatively sturdy, yet requires relatively little space.

A further object of the present invention resides in the provision of an obturating arrangement for an enclosure or envelope intended to be evacuated which permits repeated use of the same pumping orifice, thereby assuring the possibility of several pumping and re-sealing oper ations with the same obturating structure.

Still another object of the present invention resides in the provision of an obturating structure, especially for high-power electron discharge devices which may be readily manufactured, is relatively inexpensive, and assures a good permanent vacuum-tight seal notwithstanding the possibility of repeated opening and closure operations with the same obturator structure.

These and other objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawing which shows, for purposes of illustration only, one construction in accordance with the present invention during consecutive phases of its realization, and wherein FIGURE 1 is a cross sectional view of one embodiment of a closure and sealing arrangement for a vacuum-type enclosure or envelope according to the present invention, the parts thereof being shown in the position which they occupy during the pumping operation;

. entire vacuum-tight assembly,

3,193,371 Patented Aug. 3, 1965 FIGURE 2 is a cross sectional view, similar to FIG URE 1, showing the parts thereof in the respective position at the end of the pumping operation;

FIGURE 3 is a cross sectional view, similar to FIG- URES 1 and 2, showing the closed off envelope or Obtlllr ated enclosure after the pumping operation, and

FIGURE 4- is a partial cross sectional view, on an enlarged scale, showing the details of certain parts of the arrangement illustrated in FIGURES 1 to 3.

According to the present invention, the vacuum-tight envelope or enclosure is characterized in that its pumping orifice is constituted by a flared passage formed, for instance, within a metallic socket or insert member, secured to the enclosure or envelope, the diameter of the passage increasing from the inside toward the outside of the envelope, and in that the pumping orifice is closed or obturated by a metallic plug forced into the passage, whereby an intimate contact is established between the plug and the metallic insert over a relatively very narrow annular band.

The insert and the plug are made of metals having substantially the same coetiicient of expansion, at least one of the parts being made of a soft metal, for example, copper, covered by another metal, for example, gold or indium.

Referring now to the drawing wherein like reference numerals are used throughout the various views to designate corresponding parts, and more particularly to FIGURES l to 3, reference numeral 1 designates therein the vacuum-tight envelope which is provided along one of the walls thereof with a pumping orifice, formed by the conical passage 2 of a socket or insert member 3 secured to the envelope l in any suitable manner. The diameter of the passage 2 increases from the inside toward the outside of the envelope 1.

A metallic plug 4 of truncated ogival form is so dime sionedas to be able to obturate the passage 2 within the insert member 3.

The insert member 3 and the plug 4 are made of metals having essentially the same coefficient of expansion, at least one of these two parts being made of soft metal, for example, copper covered by another metal, for example, gold or indium.

In order to simplify the drawings, the layer of cover metal is not shown therein.

FIGURE 1 shows the vacuum envelope l and the plug 4 during the pumping phase during which may eventually also take place the sterilization or other treatments usually performed in the manufacture of the particular device.

During this phase, an auxiliary tube d, integral with a membrane 6 and made of flexible metal, itself closed by a plate 7, is provisionally secured to .the envelope 1 by means of a vacuum-tight joint 8.

The tubular member 5 communicates through the pipe 9 with the pumping installation P which thus pumps to a predetermined degree of vacuum the envelope 1 and the sealed to the envelope by the joint 8. During this time, a rod 10, secured to the plate 7, maintains the ogival plug 4 in proximity to the insert member 3 which is of truncated conical shape.

The following phase of the operation is shown in FIG- URE 2 in which the pumping operation has been terminate'd. During this phase, there is applied, by any appropriate means, external to the illustrated system, a pressure on the plate '7 in the direction of arrow 11 thereby compressing the elastic membrane .6 whereby the plug 4 is introduced forcibly into the socket 3.

The internal surfaces of the socket or insert member 3 and those of the plug 4 are carefully machined and finished in any suitable manner, and the contact between these two pieces is established intimately over a very narrow annular band as indicated in dash line in FIG- .two parts in question.

URE 4 and designated therein by reference numeral 13, whereby FIGURE 4 illustrates, on an enlarged scale, the Owing to these dispositions, the pumping orifice of the envelope 1 is obturated in a vacuum-tight manner.

The auxiliary tubular member 5 is thereupon withdrawn by removing the temporary joint 8, and the vacuum-tight enclosure is ready to be used.

Nevertheless, for greater safety in handling, it is preferable to protect the closure device by covering the same, for example, with a protective cap-like cover such as indicated by reference numeral 12 in FIGURE 3.

The apparatus necessary for the obturation in accordance with the present invention is simple, and the vacuum-tight enclosure realized thereby offers the following advantages:

A relatively large diameter of pumping orifice;

A reduced space requirement and relatively great sturdiness of the assembly;

Facilitated recuperation, that is, possibility to pump and re-seal the same envelope as many times as is desired, and

Possibility of high temperature sterilization.

While we have shown and described one embodiment in accordance with the present invention, it is understood that the same is not limited thereto, but is susceptible of many changes and modifications Within the spirit and scope thereof as known to a person skilled in the art. Thus, for instance, the structure according to the present invention may be modified in such a way that a conical plug engages in a socket having convex Walls. The plug may also a spherical form or any other suitable form. Additionally, the various parts may be made of any suitable material having the prerequisite characteristics outlined hereinabove.

Thus, it is obvious that the present invention is susceptible of many changes and modifications within the spirit and scope thereof, and we, therefore, do not wish to be limited to the details shown and described herein, but intend to cover all such changes and modifications as are encompassed by the scope of the appended claims.

We claim:

1. A metallic vacuum-tight envelope provided with a metallic recess having a flared exhaust passage of substantially circular cross section that increases from the inside toward the outside of the envelope, and a metallic closure plug forced into said passage to establish therein a vacuum-tight seal, the metals of said recess and plug having substantially the same coefficient of expansion, at least one of said metals being a soft metal coated with a thin layer of another metal, and the shape of said plug being such that a tight contact is established between said recess and plug over only a relatively narrow annular strip.

2. A vacuum-tight envelope according to claim 1, wherein the outer surfaces of said metallic plug engage directly the inner surfaces of said flared passage.

3. A metallic vacuum-tight envelope provided with a metallic recess having a flared exhaust passage of 'sub stantially circular cross section that increases from the inside toward the outside of the envelope, and a metallic plug forced into said passage to establish therein a vacuum-tight seal, the metals of said recess and plug having substantially the same coefficient of expansion, at least one of said metals being copper coated with a thin layer of another metal, and the shape of said plug being such that a tight contact is established between said recess and plug over only a relatively narrow annular strip.

4. A vacuum-tight envelope according to claim 3, wherein said other metal is selected from the group con sisting of indium and gold.

5. A vacuum-tight envelope according to claim 2, further comprising a protective cover disposed over said recess and plug.

References Cited by the Examiner UNITED STATES PATENTS 517,432 4/94 Carey 220-2.2 659,687 10/00 Myers 2202.2 805,131 11/05 Gerow 22O2.2 1,820,553 8/31 Berthold et al 220-22 1,839,340 1/32 Pittlick 22046 2,442,608 6/48 Iemmens et al. 220-22 2,454,572 11/48 Roovers 220-2.2 2,641,381 6/53 Bertrand 22046 THERON E. CONDON, Primary Examiner.

EARLE I. DRUMMOND, Examiner, 

1. A METALLIC VACUUM-TIGHT ENVELOPE PROVIDED WITH A METALIC RECESS HAVING A FLARED EXHAUST PASSAGE OF SUBSTANTIALLY CIRCULAR CROSS SECTION THAT INCREASES FROM THE INSIDE TOWARD THE OUTSIDE OF THE ENVELOPE, AND A METALLIC CLOSURE PLUG FORCED INTO SAID PASSAGE TO ESTABLISH THEREIN A VACUUM-TIGHT SEAL, THE METALS OF SAID RECESS AND PLUG HAVING SUBSTANTIALLY THE SAME COEFFICIENT OF EXPANSION AT LEAST ONE OF SAID METALS BEING A SOFT METAL COATED WITH A THIN LAYER OF ANOTHER METAL, AND THE SHAPE OF SAID PLUG BEING SUCH THAT A TIGHT CONTACT IS ESTABLISHED BETWEEN SAID RECESS AND PLUG OVER ONLY A RELATIVELY NARROW ANNULAR STRIP. 